In high performance aircraft of the type utilized by Armed Forces it is customary to provide the aircrewmen with headgear of the type including a visor and a breathing mask. In order to improve the safety factor of the headgear it is desirable that provision be made for defogging the visor or lens, and also that the breathing gases supplied to the aircrewmen be filtered to prevent the inhalation of harmful gases. Such equipment could utilize a single source of gases for both purposes. Alternatively, breathing gases could be supplemented by a separate source of ventilating gases. One advantage of a system utilizing separate supplies of breathing gases and ventilating gases is that if one supply should fail there is an alternate backup supply which could be utilized for both purposes.
In prior art systems which filter the breathing gas the filter has been customarily mounted on the chest of the aircrewman, the filter housing assembly being secured in some manner to the aircrewman's apparel, such as the parachute harness. A quick disconnect breathing gas supply coupling is secured to the filter housing and if the aircrewman ejects from the aircraft there will be no loose air supply hoses which could flail the aircrewman during bailout. However, separate ventilating hoses, which in the past have not been connected to the filter housing, could flail the aircrewman during bailout.